Apparatus for cooling and freezing of articles, such as foodstuffs, is well known in the prior art. Relevant prior art apparatus generally comprise elongated freezing tunnels through which articles to be cooled and frozen are passed, generally on a moving belt or other conveyor means. Long, narrow cooling and freezing tunnels are necessary to minimize crycgen requirements, yet allow for long contact times for articles or foodstuffs to be cooled or frozen. Maintenance and cleaning present a problem for such elongated tunnels, particularly with regard to interior access.
The opening of such cooling and freezing tunnels to render them readily accessible is necessary, particularly wherein foodstuffs are passed through the tunnel for cooling and freezing. In the use of such tunnels, crumbs and particles of food are frequently broken off of the food articles being moved through the tunnel and remain in the interstices of the conveyor belt or fall through the belt onto the bottom of the tunnel. Such particles, if permitted to remain in the apparatus, will become spoiled and may contaminate fresh food passing there through. Consequently, it is imperative that means be provided to facilitate cleaning of such apparatus to meet USDA standards, as well as to facilitate inspection thereof by USDA officials.
The construction of prior art apparatus, however, inherently hindered the attainment of these objectives. This was caused primarily by the fact that the tunnels had to have gas tight seals along their lengths, which rendered disassembly thereof difficult. Moreover, the length of the tunnels, often over 50 ft. long, frustrated effective hosing down from end to end.
For instance, in U.S. Pat. No. 3,813,895 a freezing tunnel is described wherein a continuous conveyor travels longitudinally through an insulated freezing tunnel refrigerated with a cryogenic fluid, such as liquid nitrogen. The freezing tunnel is designed so that a bottom and a hinged cover can be opened downwardly and pivotably upward, respectively, to gain access to the interior of the tunnel, the conveyor, and the stationary assemblies, specifically for cleaning and inspection. The actuation of the movement of the covers and bottoms of such a tunnel is performed by a series of rotary geared screw jacks driven by a drive shaft connected to an electric motor housed under the tunnel and connected to a drive shaft by geared transmission means. Despite this prior art means for opening a cooling and freezing tunnel, durable and accurate means for opening such tunnels for cleaning and inspecting repeatedly during the course of use, particularly long term use, remains to be found.
Other prior art freezing tunnels are known wherein portions of the tunnel may be opened for access. U.S. Pat. No. 3,892,104 discloses such a tunnel and details the manner for variably controlling the flow of cooling gas through the tunnel. As shown in FIG. 2 of that patent, the cooling tunnel is opened by a series of rotary geared screw jacks 24 which raise and lower the bottom of the tunnel.
Other patents of general interest to the cooling and freezing tunnel art include U.S. Pat. Nos. 1,822,077, 3,580,000, 3,583,171 and 3,757,533.
All of the prior art suffers from either a failure to provide adequate means for gaining access to the interior of an elongated cooling or freezing tunnel, or the means utilized for opening and closing an accessible freezing tunnel are not durable under the moisture and caustic conditions inherent in a tunnel that is periodically washed down and cleansed. Such prior art also is susceptible of inaccurate movement of the openable sections of the tunnel when individual rotary geared screw jacks are replaced after service is performed on the tunnel. In addition, prior art actuation means do not provide the variable force desired to open an openable freezing tunnel, wherein the initial opening force is required to exceed the normal force for movement or travel of the openable sections due to the problem of frozen and sticking components in the openable sections. The present invention overcomes these drawbacks as will be readily understood from the description below.